No I don't think it's rebellion at all. In the bible it says ashes to ashes and dust to dust. So I don't think it would be rebellious against got to get cremated.
Actually cremation is a much better way to dispose of the body than just simply burying.
Cemeteries are filling up and eventually there may not be much space to bury everyone that dies.
When I die I'm gonna be cremated. It's much cheaper too.